Apparatus for additively manufacturing three-dimensional objects

ABSTRACT

Apparatus (1) for additively manufacturing three-dimensional objects (2) by means of successive layerwise selective irradiation and consolidation of layers of a build material (3) which can be consolidated by means of an energy source (4), which apparatus (1) comprises an application unit (6) with at least one application element (7) adapted to apply build material (3) on a build plane (8), characterized in by a determination unit (12) that is adapted to determine contact information relating to a force acting on the at least one application element (7), preferably during an application process.

The invention relates to an apparatus for additively manufacturingthree-dimensional objects by means of successive layerwise selectiveirradiation and consolidation of layers of a build material which can beconsolidated by means of an energy source, which apparatus comprises anapplication unit with at least one application element adapted to applybuild material on a build plane.

Such apparatuses that provide an energy source to selectively irradiatelayers of build material to successively layerwise manufacture athree-dimensional object are generally known from prior art. Typically,build material can be applied using an application unit with at leastone application element that is adapted to apply the build material onthe build plane, e.g. by conveying build material from a dose unit to abuild unit, where the build material can be distributed to form auniform layer of build material that can afterwards be selectivelyirradiated via the energy source, in particular an energy beam, such asa laser beam or an electron beam.

Further, it is known from prior art that the quality of the applicationprocess is crucial for process quality and object quality, wherein auniform application of build material in the build plane has to beensured, because otherwise deviations in the object, such as impuritiesor deviations from a nominal mechanical behavior can occur. For example,if a layer of build material is unevenly applied on the build plane,deviations in the object can occur, as the layer that is selectivelyirradiated does not comprise the same height and geometry over therespective irradiated area.

It is an object of the present invention to provide an apparatus foradditively manufacturing three-dimensional objects, wherein theapplication of build material can be improved.

The object is inventively achieved by an apparatus according to claim 1.Advantageous embodiments of the invention are subject to the dependentclaims.

The apparatus described herein is an apparatus for additivelymanufacturing three-dimensional objects, e.g. technical components, bymeans of successive selective layerwise consolidation of layers of apowdered build material (“build material”) which can be consolidated bymeans of an energy source, e.g. an energy beam, in particular a laserbeam or an electron beam. A respective build material can be a metal,ceramic or polymer powder. A respective energy beam can be a laser beamor an electron beam. A respective apparatus can be an apparatus in whichan application of build material and a consolidation of build materialis performed separately, such as a selective laser sintering apparatus,a selective laser melting apparatus or a selective electron beam meltingapparatus, for instance. Alternatively, the successive layerwiseselective consolidation of build material may be performed via at leastone binding material. The binding material may be applied with acorresponding application unit and, for example, irradiated with asuitable energy source, e.g. a UV light source.

The apparatus may comprise a number of functional units which are usedduring its operation. Exemplary functional units are a process chamber,an irradiation device which is adapted to selectively irradiate a buildmaterial layer disposed in the process chamber with at least one energybeam, and a stream generating device which is adapted to generate agaseous fluid stream at least partly streaming through the processchamber with given streaming properties, e.g. a given streaming profile,streaming velocity, etc. The gaseous fluid stream is capable of beingcharged with non-consolidated particulate build material, particularlysmoke or smoke residues generated during operation of the apparatus,while streaming through the process chamber. The gaseous fluid stream istypically inert, i.e. typically a stream of an inert gas, e.g. argon,nitrogen, carbon dioxide, etc.

As described before, the invention relates to an apparatus foradditively manufacturing three-dimensional objects, in particular to theapplication of build material in an additive manufacturing process thatis performed on the apparatus. The invention is based on the idea that adetermination unit is provided that is adapted to determine contactinformation relating to a force acting on the at least one applicationelement, preferably during an application process. Thus, the inventiveapparatus comprises a determination unit or is connectable or connectedwith a determination unit. The inventive determination unit candetermine contact information that relate to a force acting on, e.g.applied on, the at least one application element. Hence, a force thatacts on the application element can be monitored. For example, theapplication element being moved over the build plane may come in contactwith a previously applied or previously consolidated layer of buildmaterial, i.e. a part of the object that is additively built in themanufacturing process, wherein the contact results in a force applied oracting on the application element, respectively. Also, a force acts onthe application element due to the application element conveying ordistributing the build material in the build plane, e.g. pushing thebuild material over the build plane to distribute the build material andform a fresh layer of build material.

The determination unit may therefore, determine contact information andderive (measure) the force acting on the at least one applicationelement. Thus, it can be determined whether the application process inwhich build material is applied on the build plane, is performedproperly or whether irregularities are present in the applicationprocess. For example, it is possible that due to imperfections in apreviously applied layer, for example spatters or an error in thethree-dimensional object, such as a part of the object protruding thebuild plane, the application element comes in contact with thethree-dimensional object (part of the previously consolidated layer, forinstance) or with spatters of build material that landed on the buildplane. If the application element comes in contact withthree-dimensional object, a force different from a nominal force thatwould usually act on the application element in a proper applicationprocess may be applied on the application element. Usually, the forceacting on the application element due to a contact between the objectand the application element is significantly higher than a force actingon the application element in a regular application process.

In particular, it is possible that, if the application element comes incontact with the previously applied and consolidated layer of buildmaterial or with a structure of the apparatus, such as a carryingelement carrying the build material, for instance, the applicationelement and/or the previously applied layer of the object, can bedamaged. In the worst-case, it is possible that the application elementcomes in contact with a previously applied layer of build material inthat the application process cannot be continued, as the force thatwould be required to apply build material exceeds a maximum force withwhich the application element can be moved over the build plane.Alternatively or additionally it is possible that the applicationelement and/or the previously built part of the object sustain damagedue to the contact.

By way of the invention it is possible to determine the contactinformation and therefore, to determine the force that acts on the atleast one application element. Preferably the determination is performedduring an application process, wherein the application element appliesbuild material on the build plane, wherein the contact information canbe used to derive whether the application process is performed properly.Of course, it is also possible to move the application elementindependent of an application process, for example for performing adetermination process, wherein the application element is moved over thebuild plane to determine the contact information solely.

The at least one determination unit may comprise at least onedetermination element for determining the contact information, whichdetermination element is built as or comprises

-   -   a force sensitive element, in particular a piezoelectric element        and/or a strain gauge, and/or    -   a magnetic element and/or    -   a determination element adapted to determine a deviation of the        application element from a neutral position, in particular a        laser interferometer and/or    -   an ultrasonic element.

Thus, the determination element may be built as or comprise a forcesensitive element, in particular a piezoelectric element and/or a straingauge. The force sensitive element, such as a piezoelectric element, maybe used to derive/measure the force that acts on the applicationelement. For example, a force acting on the application element may leadto a deviation of the application element from a nominal position. Theforce acting on the application element may also act on the forcesensitive element that is coupled with the application element, forexample deflecting the force sensitive element from a zero position.This may, for example, generate a voltage that can be measured todetermine force acting on the application element.

Further, it is also possible to have a determination element that isadapted to determine a deviation of the application element from aneutral position, in particular to determine a distance between theapplication element and a reference position and/or a deviation from adefined distance. For example, a laser interferometer may be used, todetermine the position of the application element or a deviation from aneutral position. For example, if the application element is deflectedfrom a neutral position via the force acting on the application element,the determination element may be adapted to determine this deviation.Hence, the force acting on the application element may be derived fromthe results of the position and/or distance determination performed viathe determination element.

According to another embodiment of the inventive apparatus, thedetermination unit may be adapted to determine the force acting on theapplication element, in particular against application direction and/orrelative to the application direction, preferably during an applicationprocess. The term “application direction” may relate to the direction inwhich the application element is moved to convey and/or distribute thebuild material in an application process performed during the additivemanufacturing process. Hence, the application direction may be deemedparallel to a machine axis. According to this embodiment, thedetermination unit can be adapted to determine a force that acts on theapplication element, for example against application direction and/orrelative to the application direction, in particular perpendicular tothe application direction. Hence, a force that is applied on theapplication element, for example with the application element moving orconveying or distributing build material in application direction or aforce that acts on the application element perpendicular to theapplication direction.

If an irregularity is present in the additive manufacturing process, inparticular in the application process, the force that acts on theapplication element in the case of an irregularity is different from theforce that usually acts on the application element during a regularapplication step. Hence, an application element that comes in contactwith a previously built layer of the object or the build plate, forinstance, will receive the force that exceeds the force that usually ispresent in a regular application process. Thus, contact information canbe determined via the determination of the force that acts on theapplication element, wherein it is possible to conclude on the effectson the process quality and/or the object quality via the contactinformation.

In particular, it is possible that the determination unit may be adaptedto determine whether the application element is or will be or was incontact with a previously built layer of the three-dimensional objectbased on the contact information. As described before, it is possible todetermine the force that acts on the application element. If theapplication element was or is in contact with a previously built layerof the object, the force that acts or acted on the application elementin the situation will differ from a regular force acting on theapplication element in a proper application process. Thus, via thecontact information the determination unit is adapted to determinewhether the application element is or was in contact with a previouslybuilt layer of the three-dimensional object. It is also possible thatthe determination unit is adapted to determine whether the applicationelement will be in contact with a previously built layer ofthree-dimensional object, wherein the contact information can be derivedsimultaneously while the application element is used to apply buildmaterial on the build plane. If a rise in the force acting on theapplication element is determined, it can be derived whether or when theapplication element will be in contact with a previously built layer ofthe three-dimensional object. Thus, it is possible to stop theapplication process before the three-dimensional object and/or theapplication element receive damage.

The inventive apparatus can further be improved in that a control unitis provided that is adapted to control the movement of the at least oneapplication element, in particular dependent on the contact information.According to this embodiment, a control unit can be provided, forexample a control unit integrated in the apparatus, which control unitis adapted to control the movement of the at least one applicationelement. The control of the movement of the at least one applicationelement may particularly be performed dependent on the determinedcontact information, wherein it is possible to use the determinedcontact information, i.e. to improve the application process. Forexample, dependent on the contact information, in particular the forcethat acts on the application element, it is possible to derive whetherthe application process is performed properly or whether an adjustmentto the movement of the application element is necessary. The force thatacts on the application element, in particular a force componentoriented against the application direction, may indicate the amount ofbuild material that is conveyed via the application element. If theamount of build material deviates from a nominal amount, surplus buildmaterial is increased that is wasted in the additive manufacturingprocess, wherein it is possible to adjust the amount of build materialthat is conveyed via the application element based on the contactinformation. It is also possible to adjust the position of theapplication element relative to the at least one previously built layerof build material, for example, if it is indicated via the contactinformation and, e.g., the application element is moved to close to thebuild plane.

The control unit may preferably be adapted to store the contactinformation in a data storage device. A data storage device can compriseor be built as any arbitrary device that is adapted to store the contactinformation, such as a hard drive. The stored contact information canlater be read, i.e. used, for example for quality management purposes.For example, the stored contact information, preferably stored for everylayer of build material that has been applied in the additivemanufacturing process, can be used to verify that the applicationprocess has been performed without irregularities. Thus, the contactinformation can be used as quality indicator to ensure that theapplication element has not come in contact with other thannon-consolidated build material that has been applied via theapplication element in the build plane.

The control unit may also be adapted to relate the contact informationto the additive manufacturing process, in particular adapted to relatethe contact information to at least one part of the three-dimensionalobject, in which the application unit is or was in contact with thecorresponding layer of the object in the additive manufacturing process.In other words, it is possible that a direct relation between thecontact information and the additively built object can be established.For example, it is possible to relate the contact information that hasbeen determined in the additive manufacturing process to the at leastone part of the three-dimensional object that was currently built whenthe contact information has been determined. For instance, the contactinformation that is determined during the application of build materialin a specific layer of the three-dimensional object, can be related tothat specific layer and indicate, whether an irregularity has beenpresent during the application of build material. Based on the contactinformation, it is possible to verify that the quality of theapplication process and therefore, the object quality of thethree-dimensional object that is built in the additive manufacturingprocess meets predefined requirements.

On the other hand, it is also possible to derive whether the applicationelement received a regular force in the application process andtherefore, it is possible to use the contact information to relateirregularities to specific layers of the object, for example toindicate, whether a post-process, such as a non-destroying analysis ofthe object is deemed necessary. It is also possible to monitor or,whether weld spatters or the like were present in the additivemanufacturing process. Said weld spatters may be generated in a directlyirradiated part of the build plane, in particular in a meltpool, withthe energy source irradiating and heating build material in that thebuild material is liquidized and tends to form spatters. The spattersfall back on the build plane and can cause irregularities in theadditive manufacturing process. If the application element comes incontact with those spatters, a deviation from a nominal force can bereceived or measured via the corresponding determination element. Thus,the contact information may give rise about whether spatters are/werepresent in the additive manufacturing process.

Further, the control unit may be adapted to generate a map, inparticular a three-dimensional map, indicating, i.e. spatiallyresolving, the contact information in relation to the three-dimensionalobject. Thus, it is possible to have the control unit spatially resolvethe contact information in relation to the geometry of thethree-dimensional object. In particular, it is possible to spatiallyresolve the contact information for each layer of the three-dimensionalobject in a three-dimensional map. In other words, the three-dimensionalmap comprises the contact information for several layers of the object,wherein for each position of the application element it is possible tostore the contact information, e.g. the force acting on the applicationelement in this position, in the three-dimensional map. Thus, it can beidentified in which position a deviation from a nominal force acted onthe application element and in which position therefore, the applicationprocess may comprise an irregularity. Thus, dependent on the quality ofthe application process that is indicated via the three-dimensional mapcomprising the contact information, it can be decided whether apost-process, such as a computer tomography of the three-dimensionalobject needs to be performed.

Advantageously, the control unit may be adapted to generate qualityinformation relating to the object quality of the three-dimensionalobject based on the contact information. As described before, thecontact information may indicate whether the application process hasbeen performed properly or whether irregularities happened in theapplication of build material via the application element. Thus, if noirregularities were found based on the contact information, the controlunit may generate quality information indicating that the applicationprocess of the object has been performed properly. Otherwise, it ispossible to generate quality information indicating that, for example,the application element came in contact with a previously built part ofthree-dimensional object or weld spatters or the like resulting in anincrease of the force acting on the application element were determined.

According to another embodiment of the inventive apparatus, the controlunit may be adapted to define and/or to receive a quality criteriondefining a value or a value range dependent on which the qualityinformation may be generated. For example, it is possible that a userdefines a quality criterion for the contact information, such as anominal force or a nominal force range, based on which qualityinformation can be generated. In particular, if the contact informationthat is determined lies within the value range or meets the value thathas been received or defined via the control unit, the qualityinformation can indicate that the three-dimensional object isqualitatively acceptable or fulfills defined quality requirements.Otherwise, the quality information may indicate that a predefinedquality requirement is not met or that a post-processing of theadditively built object is necessary.

The control unit of the inventive apparatus may further be adapted todetermine whether a replacement of the at least one application elementis necessary, in particular to determine and indicate a necessaryreplacement. For example, if the contact information indicates that theapplication element was in contact with a previously built layer of thethree-dimensional object, or a weld spatter, for instance, theapplication element may have received damage that can compromise futureapplication processes in that it is necessary to replace the applicationelement with a fresh or new application element, such as a recoaterblade. Thus, dependent on the contact information the control unit candecide whether the application element has to be replaced. Inparticular, the force acting on the application element can be monitoredand, if the force acting on the application element exceeds apredefined, in particular user-defined, value, a replacement of theapplication element can be deemed necessary or can automatically beperformed, respectively.

The control unit may further be adapted to generate applicationinformation relating to the quality of an application process, dependenton the contact information. Thus, the control unit may derive whetherthe application process meets predefined application qualityrequirements based on the contact information. For example, if thecontact information indicates that a force acting on the applicationelement during an application process exceeded a predefined value, inparticular a predefined force value was exceeded, the quality of theapplication process may be deemed as not fulfilling predefined qualityrequirements.

According to another embodiment of the inventive apparatus, the controlunit may be adapted to adjust at least one process parameter dependenton the contact information, in particular a layer thickness and/or amovement parameter of the at least one application element and/or atleast one irradiation parameter and/or at least one position of the atleast one application element. Thus, it is possible to determine thecontact information and adjust at least one process parameter dependenton the contact information. For example, the contact information may beused to derive information relating to the melting track, wherein theprocess parameters may be improved until the melting track meetspredefined requirements. For example, irradiation parameters may beadjusted to find optimal parameters to improve the melting track. Themelting track directly influences the force that acts on the applicationelement during an application process of build material on thepreviously applied and consolidated layer of build material comprisingthe previously consolidated melting track. It is also possible to adjustvarious other process parameters other than irradiation parameters, suchas application parameters, i.e. a layer thickness and/or a movementparameter, for example the velocity with which the application elementis moved over the build plane.

Besides, the invention relates to a determination unit for an apparatusfor additively manufacturing three-dimensional objects, in particular aninventive apparatus, as described before, wherein the determination unitis adapted to determine a contact information relating to a force actingon the at least one application element.

Further, the invention relates to a method for operating at least oneapparatus for additively manufacturing three-dimensional objects bymeans of successive layerwise selective irradiation and consolidation oflayers of a build material which can be consolidated by means of anenergy source, in particular an inventive apparatus, as describedbefore, wherein a contact information relating to a force acting on theat least one application element is determined.

Self-evidently, all features, details and advantages described withrespect to the inventive apparatus are fully transferable to theinventive determination unit and the inventive method.

Exemplary embodiments of the invention are described with reference tothe FIG.

The Fig. are schematic diagrams, wherein

FIG. 1 shows an inventive apparatus; and

FIG. 2 shows an inventive apparatus.

FIG. 1 shows an apparatus 1 for additively manufacturingthree-dimensional objects 2 by means of successive layerwise selectiveirradiation and consolidation of layers of a build material 3 which canbe consolidated by means of an energy source 4. The apparatus 1comprises an energy source 4 (irradiation device) that is adapted toirradiate the build material 3, e.g. adapted to generate an energy beam5, such as a laser beam or an electron beam, for instance. The apparatus1 further comprises an application unit 6 with an application element 7that is adapted to apply build material 3 on a build plane 8. The buildplane 8 is a plane in which build material 3 is arranged, wherein thebuild material 3 arranged in the build plane 8 can be selectivelyirradiated with the energy beam 5, dependent on the control of theenergy beam 5 that is performed via the energy source 4.

In other words, the application unit 6 can guide the application element7 over the build plane 8, e.g. a powder bed, in particular carried via acarrying element 9, to apply a fresh layer 10 of build material 3 onto apreviously applied layer or onto the carrying element 9, respectivelythe carrying element 9 may also be deemed as “build plate”. Thus, buildmaterial 3 can be applied in a layerwise manner, wherein the buildmaterial 3 is distributed as a layer 10 arranged in the build plane 8.Dependent on the movement of the carrying element 7, a layer thickness(indicated via arrow 11) can be defined.

The apparatus 1 further comprises a determination unit 12 that isadapted to determine contact information relating to a force acting onthe application element 7, preferably during an application process.Thus, it is possible to determine a force that acts on the applicationelement 7, preferably while the application element 7 is moved over thebuild plane 8 to convey and distribute build material 3 in the buildplane 8, i.e. to form a fresh layer 10 in the build plane 8. Hence, viathe application unit 6 fresh layers 10 of build material 3 can beapplied successively and can be irradiated via the energy source 4 toselectively consolidate the build material 3 to form the object 2.

The application element 7 is coupled with a determination element 13,for example a piezoeletric element. Dependent on the force that acts onthe application element 7 the determination element 13 is adapted togenerate a signal that can be sent or can be received via thedetermination unit 12. Dependent on the determined force (or thecorrelated signal), the contact information can be determined. Thedetermination element 13 is adapted to determine forces that act on theapplication element 7, for instance perpendicular (indicated via arrow16) to an application direction (indicated via arrow 17) and/or against(indicated via arrow 18) application direction. The term “applicationdirection” refers to the direction in which the application element 7 ismoved to apply build material 3.

The apparatus 1 further comprises a control unit 14 that is adapted tocontrol the movement of the application element 7, in particulardependent on the contact information. The determined contact informationcan further be stored in a data storage 15, for example stored as athree-dimensional map spatially resolving the contact information andthereby relating the contact information to at least one part of thethree-dimensional object 2. The control unit 14 is further adapted togenerate quality information relating to object quality of thethree-dimensional object 2 based on the contact information and/or togenerate application quality relating to the quality of an applicationprocess in which a layer 10 of build material 3 is applied on the buildplane 8.

Dependent on the contact information it is also possible that thecontrol unit 14 may adjust at least one process parameter, for examplethe layer thickness 11 and/or a movement parameter of the applicationelement 7 and/or at least one irradiation parameter and/or at least oneposition of the application element 7. Thus, it is possible to adjustprocess parameters and find optimal process parameters based on thecontact information. For example, irradiation parameters based on whichthe energy source 4 generates the energy beam 5, such as spot sizeand/or power and/or intensity and/or a scan speed, can be varied,wherein an optimal process parameter can be determined dependent on thecontact information. As the contact information relates to the forcethat is applied or that acts on the application element 7, animprovement of a process parameter can be found by determining the forceacting on the application element 7. The at least one process parameteris improved, if a lower force acts on the application element 7 comparedwith a previous process parameter. The lowest force acting on theapplication element 7 compared with an initial process parameter may bedeemed as optimal parameter.

FIG. 2 shows the apparatus 1 in another situation. Therefore, samereference signs are used for same parts. In the situation that isdepicted in FIG. 2 the application unit 6, in particular the applicationelement 7 is moved over the build plane 8 to apply a fresh layer 10 ofbuild material 3. Due to deviations of the object 2, a part 19 of theobject 2 is not even and sticks out of the build plane 8. Thus, thecontact information may indicate an irregularity in the applicationprocess, in particular a comparatively higher force acting on theapplication element 7. The determined force may in particular comprise aforce component perpendicular (arrow 16) to the application direction(arrow 17). Hence, the determination unit 12 determines the contactinformation and is adapted to send the contact information to thecontrol unit 14 that is adapted to determine whether the applicationelement 7 is or was in contact with the part 19 of the object 2. Thepart 19 may, in particular, be or comprise a previously built layer ofbuild material 3.

Thus, the control unit 14 may decide whether a replacement of theapplication element 7 is necessary due to a potential contact betweenthe application element 7 and the part 19. Based on the contactinformation it is further possible to generate quality information andstore the contact information, in particular in the form of athree-dimensional map in the data storage device 15, as describedbefore. Hence, it is possible to relate the contact information to theobject 2 and spatially resolve the contact information for each layer 10of the object 2. Thus, it is possible that, e.g. a user, can have thecontact information visualized in the three-dimensional map, such as athree-dimensional model of the object 2 that was additively built in theadditive manufacturing process performed on the apparatus 1. The usermay therefore, derive from the contact information areas of the object 2in which the contact information indicates irregularities theapplication process, in particular higher than usual forces acting onthe application element 7.

Therefore, it is possible to decide whether a post-processing of theobject 2, for example via non-destroying analysis, such as computertomography, is deemed necessary. It is also possible to replace theapplication element 7, if a contact between the application element 7and the part 19 has been determined to avoid a negative impact on futureapplication process due to the application element 7 being damaged dueto the contact with the object 2. Thus, a damaged application element 7compromising further application processes, as the damage in theapplication element 7 degrades application quality, can be avoided byreplacing the application element 7 in advance to the next applicationstep.

Self-evidently, the inventive method may be performed on the inventiveapparatus 1, preferably using an inventive determination device 12.

1. Apparatus (1) for additively manufacturing three-dimensional objects(2) by means of successive layerwise selective irradiation andconsolidation of layers of a build material (3) which can beconsolidated by means of an energy source (4), which apparatus (1)comprises an application unit (6) with at least one application element(7) adapted to apply build material (3) on a build plane (8),characterized in by a determination unit (12) that is adapted todetermine contact information relating to a force acting on the at leastone application element (7), preferably during an application process.2. Apparatus according to claim 1, characterized in that the at leastone determination unit (12) comprises at least one determination element(13) for determining the contact information, which determinationelement (13) is built as or comprises a force sensitive element, inparticular a piezoelectrical element and/or a strain gauge, and/or amagnetic element and/or a determination element (13) adapted todetermine a deviation of the application element (7) from a neutralposition, in particular a laser interferometer and/or an ultrasonicelement.
 3. Apparatus according to claim 1, characterized in that thedetermination unit (12) is adapted to determine a force acting on theapplication element (7), in particular against application direction(17) and/or relative to the application direction (17), preferablyduring an application process.
 4. Apparatus according to claim 1,characterized in that the determination unit (12) is adapted todetermine whether the application element (7) is or will be or was incontact with a previously built layer (10) of the three-dimensionalobject (2) based on the contact information.
 5. Apparatus according toclaim 1, characterized in that a control unit (14) is provided that isadapted to control the movement of the at least one application element(7), in particular dependent on the contact information.
 6. Apparatusaccording to claim 5, characterized in that the control unit (14) isadapted to store the contact information in a data storage device (15).7. Apparatus according to claim 5, characterized in that the controlunit (14) is adapted to relate the contact information to the additivemanufacturing process, in particular adapted to relate the contactinformation to at least one part (19) of the three-dimensional object(2), in which the application element (7) is or was in contact with thecorresponding layer of the object (2) in the additive manufacturingprocess.
 8. Apparatus according to claim 5, characterized in that thecontrol unit (14) is adapted to generate a map, in particular athree-dimensional map, spatially resolving the contact information inrelation to the three-dimensional object (2).
 9. Apparatus according toclaim 5, characterized in that the control unit (14) is adapted togenerate quality information relating to object quality of thethree-dimensional object (2) based on the contact information. 10.Apparatus according to claim 5, characterized in that the control unit(14) is adapted to define and/or to receive a quality criterion defininga value or a value range dependent on which the quality information isgenerated.
 11. Apparatus according to claim 5, characterized in that thecontrol unit (14) is adapted to determine whether a replacement of theat least one application element (7) is necessary, in particular todetermine and indicate a necessary replacement.
 12. Apparatus accordingto claim 5, characterized in that the control unit (14) is adapted toadjust at least one process parameter dependent on the contactinformation, in particular a layer thickness and/or a movement parameterof the at least one application element (7) and/or at least oneirradiation parameter and/or at least one position of the at least oneapplication element (7).
 13. Apparatus according to claim 5,characterized in that the control unit (14) is adapted to generateapplication information relating to the quality of an applicationprocess, dependent on the contact information.
 14. Determination unit(12) for an apparatus (1) for additively manufacturing ofthree-dimensional objects (2), in particular an apparatus (1) accordingto claim 1, characterized in that the determination unit (12) is adaptedto determine a contact information relating to a force acting on the atleast one application element (7).
 15. Method for operating at least oneapparatus (1) for additively manufacturing three-dimensional objects (2)by means of successive layerwise selective irradiation and consolidationof layers of a build material (3) which can be consolidated by means ofan energy source (4), in particular an apparatus (1) according to claim1, characterized in that a contact information relating to a forceacting on the at least one application element (7) is determined.